This invention relates generally to down hole tools and methods for manufacturing such items. More particularly, this invention relates to infiltrated matrix drilling products including, but not limited to, matrix drill bits, bi-center bits, core heads, and matrix bodied reamers and stabilizers, and the methods of manufacturing such items.
Full hole tungsten carbide matrix drill bits for oilfield applications have been manufactured and used in drilling since at least as early as the 1940's. FIG. 1 shows a cross-sectional view of a down hole tool casting assembly 100 in accordance with the prior art. The down hole tool casting assembly 100 consists of a mold 110, a stalk 120, one or more nozzle displacements 122, a blank 124, a funnel 140, and a binder pot 150. The down hole tool casting assembly 100 is used to fabricate a casting (not shown) of a down hole tool.
According to a typical casting method as shown in FIG. 1, the mold 110 is fabricated with a precisely machined interior surface 112, and forms a mold volume 114 located within the interior of the mold 110. The interior surface 112 at least partially surrounds the mold volume 114. The mold 110 is made from sand, hard carbon graphite, or ceramic. The precisely machined interior surface 112 has a shape that is a negative of what will become the facial features of the eventual bit face. The precisely machined interior surface 112 is milled and dressed to form the proper contours of the finished bit. Various types of cutters (not shown), known to persons having ordinary skill in the art, can be placed along the locations of the cutting edges of the bit and can also be optionally placed along the gauge area of the bit. These cutters can be placed during the bit fabrication process or after the bit has been fabricated via brazing or other methods known to people having ordinary skill in the art.
Once the mold 110 is fabricated, displacements are placed at least partially within the mold volume 114 of the mold 110. The displacements are typically fabricated from clay, sand, graphite, or ceramic. These displacements consist of the center stalk 120 and the at least one nozzle displacement 122. The center stalk 120 is positioned substantially within the center of the mold 110 and suspended a desired distance from the bottom of the mold's interior surface 112. The nozzle displacements 122 are positioned within the mold 110 and extend from the center stalk 120 to the bottom of the mold's interior surface 112. The center stalk 120 and the nozzle displacements 122 are later removed from the eventual drill bit casting so that drilling fluid can flow though the center of the finished bit during the drill bit's operation.
The blank 124 is a cylindrical steel casting mandrel that is centrally suspended at least partially within the mold 110 and around the center stalk 120. A tooling (not shown), which is known to people having ordinary skill in the art, is used to suspend the blank 124 within the mold 110. The blank 124 is hanged on the tooling and the tooling is lowered so that the blank 124 is positioned a predetermined distance down into the mold 110 and aligned appropriately therein as desired. This procedure is performed each time a down hole tool that utilizes a blank is fabricated. This process is very time consuming to ensure that the blank 124 is correctly positioned, both height and orientation, within the mold 110; and is thus, a very expensive process.
Once the displacements 120, 122 and the blank 124 have been properly positioned within the mold 110, tungsten carbide powder 130 is loaded into the mold 110 so that it fills a portion of the mold volume 114 that includes an area around the lower portion of the blank 124, between the inner surfaces of the blank 124 and the outer surfaces of the center stalk 120, and between the nozzle displacements 122. Shoulder powder 134 is loaded on top of the tungsten carbide powder 130 in an area located at both the area outside of the blank 124 and the area between the blank 124 and the center stalk 120. The shoulder powder 134 can be made of tungsten powder. This shoulder powder 134 acts to blend the casting to the steel and is machinable. Once the tungsten carbide powder 130 and the shoulder powder 134 are loaded into the mold 110, the mold 110 is typically vibrated to improve the compaction of the tungsten carbide powder 130 and the shoulder powder 134. Although the mold 110 is vibrated after the tungsten carbide powder 130 and the shoulder powder 134 are loaded into the mold 110, the vibration of the mold 110 can be done as an intermediate step before the shoulder powder 134 is loaded on top of the tungsten carbide powder 130. Additionally, the vibration of the mold 110 can be done as an intermediate step before the shoulder powder 134 is loaded on top of the tungsten carbide powder 130 and after the shoulder powder 134 is loaded on top of the tungsten carbide powder 130.
The funnel 140 is a graphite cylinder that forms a funnel volume 144 therein. The funnel 140 is coupled to the top portion of the mold 110. A recess 142 is formed at the interior edge of the bottom portion of the funnel 140, which facilitates the funnel 140 coupling to the upper portion of the mold 110. Although one example has been provided for coupling the funnel 140 to the mold 110, other methods known to people having ordinary skill in the art can be used. Typically, the inside diameter of the mold 110 is similar to the inside diameter of the funnel 140 once the funnel 140 and the mold 110 are coupled together.
The binder pot 150 is a cylinder having a base 156 with an opening 158 located at the base 156, which extends through the base 156. The binder pot 150 also forms a binder pot volume 154 therein for holding a binder material 160. The binder pot 150 is coupled to the top portion of the funnel 140 via a recess 152 that is formed at the exterior edge of the bottom portion of the binder pot 150. This recess 152 facilitates the binder pot 150 coupling to the upper portion of the funnel 140. Although one example has been provided for coupling the binder pot 150 to the funnel 140, other methods known to people having ordinary skill in the art can be used. Once the down hole tool casting assembly 100 has been assembled, a predetermined amount of binder material 160, which is ascertainable by people having ordinary skill in the art, is loaded into the binder pot volume 154. The typical binder material 160 is a copper alloy.
The down hole tool casting assembly 100 is placed within a furnace (not shown). The binder material 160 melts and flows into the tungsten carbide powder 130 through the opening 158 of the binder pot 150. In the furnace, the molten binder material 160 infiltrates the tungsten carbide powder 130. During this process, a substantial amount of binder material 160 is used so that it also fills at least a substantial portion of the funnel volume 144 located above the shoulder powder 134. This excess binder material 160 in the funnel volume 144 supplies a downward force on the tungsten carbide powder 130 and the shoulder powder 134. Once the binder material 160 completely infiltrates the tungsten carbide powder 130, the down hole tool casting assembly 100 is pulled from the furnace and is controllably cooled. The mold 110 is broken away from the casting. The casting then undergoes finishing steps which are known to people having ordinary skill in the art, including the addition of a threaded connection (not shown) coupled to the top portion of the blank 124 and the removal of the binder material 160 that filled at least a substantial portion of the funnel volume 144.
In view of the foregoing discussion, need is apparent in the art for improving the casting process so that the costs associated with casting fabrication are decreased. Additionally, a need is apparent for improving the casting process so that the costs associated with positioning the blank, both the height and the orientation, within the mold is decreased. Further, a need is apparent for improving the casting process so that the positioning of the blank, both the height and the orientation, within the mold is less time consuming. Furthermore, a need is apparent for improving the casting process so that the positioning of the blank, both the height and the orientation, within the mold is more consistent. A technology addressing one or more such needs, or some other related shortcoming in the field, would benefit down hole drilling, for example fabricating castings more effectively and more profitably. This technology is included within the current invention.